Fastener



FIG. 1 is a perspective view of a fastener, showing my new design;

FIG. 2 is a front elevational view thereof, the rear elevational view being identical;

FIG. 3 is a side elevational view thereof; and,

FIG. 4 is a bottom plan view thereof.

The dotted line disclosure of elements in the views is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a fastener, as shown and described. 